1. Field of Invention
In most running, walking, and jumping activities, the return force resulting from foot strikes causes great shock to the body. Repeated foot strikes place great stress on joints and bones, and can cause injuries to the lower back and the rotating joints of the legs. To minimize injury to the body resulting from repeated foot strikes, and also to improve athletic performance, shoe engineers have designed various spring-cushioned shoes. The springs in spring-cushioned shoes are designed to reduce shock to the body during a foot strike, and also to recover and return impact energy to the user.
One type of spring-cushioned shoe is described in U.S. Pat. No. 6,282,814 to Krafsur et al., which is incorporated herein by reference.